PDCP HFN Resynchronization Using Missing-PDU Count References
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing hyper frame number (HFN) synchronization for Packet Data Convergence Protocol (PDCP) Protocol Data Units (PDUs, leading to deciphering failures and PDCP PDU discards, particularly in scenarios with gaps exceeding the PDCP window size.
Innovation Solution
A wireless communication device calculates the current PDCP count based on the PDCP sequence number (SN) and HFN of a missing PDU to synchronize HFN, enabling deciphering operations and reducing mismatches, which includes maintaining separate HFNs for different radio access technologies in dual connectivity scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If PDCP reordering is enabled to allow out-of-order delivery of PDCP PDUs, then delivery flexibility is improved, but HFN synchronization complexity increases leading to deciphering failures
Solution Approach 1:
The patent applies preliminary action by calculating the HFN offset in advance based on the gap between expected and actual PDCP counts before deciphering operations occur. This pre-calculation of HFN adjustment ensures that when PDCP PDUs are processed out-of-order, the HFN is already corrected to the proper value, preventing deciphering failures while maintaining delivery flexibility.
2Reliability
If HFN resynchronization is performed frequently to maintain synchronization, then deciphering reliability is improved, but processing complexity and time consumption increase
Solution Approach 1:
The patent applies self-service by enabling the PDCP entity to automatically detect and correct HFN mismatches using its own stored HFN value and the received PDCP count. The entity self-adjusts the HFN offset based on the gap between expected and actual counts, eliminating the need for external intervention or complex resynchronization procedures while maintaining high deciphering reliability.
3Measurement precision
If HFN offset calculation is performed for every PDCP PDU, then synchronization precision is improved, but processing time increases
Solution Approach 1:
The patent applies partial action by calculating the HFN offset only when necessary - specifically when a gap is detected between the expected PDCP count and the actual received count. Instead of continuously adjusting HFN for every PDCP PDU, the system performs the calculation selectively at critical points where synchronization is needed, reducing processing time while maintaining precise synchronization.
Data Source
AI summary
Aspects of the present disclosure provide mechanisms for fast hyper frame number (HFN) resynchronization of Packet Data Convergence Protocol (PDCP) Protocol Data Units (PDUs). A wireless communication device (e.g., a PDCP entity at a wireless communication device) can calculate a current PDCP count of a current PDCP PDU of a plurality of PDCP PDUs received from a radio link control (RLC) sublayer based on a PDCP sequence number (SN) of the current PDCP PDU and an HFN of a first missing PDCP PDU after a successfully received PDCP PDU. The PDCP count may be calculated using the HFN of the first missing PDCP PDU in response to a gap between the PDCP count of the first missing PDCP PDU and the actual PDCP count of the current PDCP PDU being greater than a PDCP window size.